If you do not want your children to put on excess weight that could be harmful to their health, then make sure there's no TV in their bedroom. A new study has found that children's weight is influenced by whether or not they have a television in their bedroom.

 In the research "Association of a Television in the Bedroom With Increased Adiposity Gain in a Nationally Representative Sample of Children and Adolescents" published in the JAMA Pediatrics March 3, researchers involved more than 3,000 children who were between the ages 10 and 14.

The researchers asked the children's parents of their child's weight and height at the beginning of the study, after two years and after four years. The children's body mass index (BMI) was calculated as well.

The children, on the other hand, were asked if they have a TV in their bedroom and were surveyed for the number of hours they usually spend watching TV during school days, the number of hours they usually spend playing video or computer games during school days and how many movies they watch on TV per week.

The researchers found that the children who have TV sets in their bedroom gained more weight during the four year study than kids without TV in their bedroom regardless of the amount of time they spend on television viewing.

"We found that even after accounting for TV viewing, having a TV in the bedroom is associated with about one extra pound of weight gain a year," said study author Diane Gilbert-Diamond of Geisel School of Medicine at Dartmouth. "We presume that kids with a TV in their bedrooms are watching them. But having the TV in the bedroom, no matter how much TV they're watching, is associated with more weight gain."

The researchers said that the association between weight gain and having TV in the bedroom has something to do with disrupted sleep. The kids with TV in their bedroom, for instance, may stay up late to watch TV or may have poor quality of sleep after exposure to the TV's bright screen.

"Having a bedroom television is associated with weight gain beyond the effect of television viewing time. This association could be the result of uncaptured effects of television viewing or of disrupted sleep patterns," the researchers wrote. "With the high prevalence of bedroom televisions, the effect attributable to this risk factor among US children and adolescents is excess weight of 8.7 million kg/y."